Heated screed assembly



Nov. 22, 1966 J. D. LAYTON HEATED SCREED ASSEMBLY Filed Aug. 4, 1964 J c1 c k D. Lag `fon 1NVENTOR.

United States Patent 3,286,606 HEATED SCREED ASSEMBLY Jack D. Layton, Salem, Greg., assignor to Layton Manufacturing Co., Salem, Oreg., a corporation of Oregon Filed Aug. 4, 1964, Ser. No. 387,297 7 Claims. (Cl. 94-45) This invention -relates to paving apparatus, and more particularly to means for heating a screed assembly in a paver provided for the purpose of leveling and smoothing paving material.

A common form of paving apparatus may include a hopper for holding aggregate, having an opening along its base through which the material flows on being deposited on the surface being paved. A screed assembly behind the hopper trails this opening, which functions to level, smooth, and compact the freshly laid aggregate. The paver travels over the surface being paved, with movement resulting either by reason of its being towed by a truck, or by operation of its own power plant if the paver is self-propelled. To obtain optimum results, while the paver moves the screed assembly should slide smoothly over the freshly deposited aggregate.

Road-paving aggregate commonly may contain a large proportion of asphaltic or bituminous material which becomes less viscous when heated. In order that such aggregate spread smoothly, the material normally is heated before being laid down on the surface being paved. After a paving operation has been carried on for a certain amount of time, heat retained in the aggregate passing under the screed assembly eventually will cause the screed assembly to reach a temperature where it will slide smoothly over the .aggregate without sticking. However, on sta-rting up a paving operation, or if aggregate should for some reason have too low a temperature, or should weather conditions prevailing during the paving operation be extremely cold, it has been found necessary to heat the screed assembly to inhibit sticking and prevent resulting pulling and other impairment of the pavement being prepared.

This invention generally contemplates as an object thereof the provision of improved means for heating a screed assembly in a paver or similar machine, which generally may be characterized by being highly reliable, simple to operate, and easy to maintain.

Another object is to provide novel heating means for a screed assembly which is relatively fast acting, and utilizes hot gases emanating directly from a burner unit to produce heating.

The usual screed assembly includes a screed plate having a flat, relatively expansive bottom surface that slides over the material being smoothed. Means employed to heat such a plate in the past often have produced localized hot spots in the screed plate, and warping and bending because of nonuniform heat expansion effects. This, of course, is highly undesirable in any device intended to make smooth, even surfaces. A further object of the invention is to provide unique heating means for a screed plate which produces relatively uniform expansion in the plate, and features a novel heating system for margins of the plate which inhibits warping and bending.

A further object is to provide aunique form of screed heater which is readily controlled by the operator of a paver, and easilystarted up after a period of nonoperation.

The heater of the invention is relatively economical to operate, and it may be incorporated with a paver at relatively low cost.

These and other objects and advantages are attained by the invention, and the same is described hereinbelow in conjunction with the accompanying drawings, wherein:

FIG. 1 is a top plan View, with portions broken away,

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illustrating a screed assembly that may trail a hopper in a paving machine according to the invention, the screed assembly being equipped with a pair of screed heaters as contemplated herein;

FIG. 2 is a cross sectional view taken generally along the line 2*2 in FIG. 1, further illustrating details of a screed heater;

FIG. 3 is a cross sectional view, taken generally along the line 3-3 in FIG. 2, showing a screed heater in side elevation;

FIG. 4 is a cross sectional view, somewhat enlarged, of a heat-diffusing tube in the screed heater; and

FIG. 5 is a cross sectional view, also somewhat enlarged, along the line 5 5 in FIG. 3.

Referring now to the drawings, and more particularly to FIGS. 1 and 2, rear portions of .a paver 10 are shown, including the rear wall of a hopper in the paver partially shown at 12, and pivotally connected to this rear wall and trailing the hopper a screed assembly generally indicated at 14. The paver may be of the type that is towed behind the rear end of a dump truck,'and during paving of a surface, aggregate, including a large proportion of asphaltic or bituminous material, is dumped from the truck into the hopper whence the same llows through an opening at the base of the hopper to be deposited as a relatively thin layer over the surface being paved. The screed assembly shown .at 14 moves over this layer of material directly after the same has been deposited by the hopper, and functions to smooth, level, and compact it, thus to produce nished pavement. A paver of this description is more fully disclosed in copending applications entitled Apparatus for Attaching Trailing and Lead Vehicles, led August 3, 1964, and having Serial No. 387,298, and Lift Mechanism, led April 30, 1964, and having Serial No. 363,928, and now Patent No. 3,237,539.

As above indicated, a feature of this invention is the provision of novel means for heating the screed assembly when such is necessary to prevent the asphaltic or bituminous material in the aggregate from sticking to the bottom of the screed assembly. Heating of the screed assembly is performed by a pair of screed heaters indicated generally at 16 and 18, which are mounted on the -screed assembly one adjacent each end thereof. The screed heaters are similar in construction and only one of them, namely, screed heater 16, will be described in detail.

Screed assembly 14 4comprises a screed .plate 20 with an expansive Hat-bottomed surface 20a which slides over and compact-s the freshly deposited aggregate. Adjacent the forward edge of and joined to the screed plate is a wall 22, which extends substantially vertically upwardly from its location of joinder with the screed plate. Opposite Wall 22, and joined to the rear edge of the screed plate, is a vertical flange 24. 'I'his flange, and flanges 26, 28 joined to the ends of the screed plate and extending upwardly therefrom, in combination with lower portions of wall 22 bound an elongated chamber of rectangular outline disposed over the top of screed plate 20, shown at 29.

In the paver construction illustrated, wall 22 of the screed assembly is utilized to connect the screed assembly to the rear of the hopper. Thus, and as shown in FIG. 2, pivot assemblies 30 interconnect a ledge 32 on the top of wall 22 with hopper 12. In FIG. 1 t-hese pivot assemblies are obscured by posts 34 joined to hopper wall 12 projecting rearwardly of the wall. The posts have screwactuated mechanism 36 supported at their rear ends,` connected to screed assemlbly 14, utilized in changing the angular position of the screed assembly relative to rear hopper wall 12.

Considering now the construction of a screed heater, and referring to FIGS. 1-5, and with particular references to heater 16, it will be noted that the heater comprises a pair of elongated Iheat-diffusing conduits or tubes 40, 42 with closed ends which extend longitudinally of screed plate 20 within the chamber bounded by flanges 24, 26, 28 and wall 22. The tubes are disposed closely adjacent the top of the screed plate, a slight distance inwardly in the screed assembly from flange 24 and wall 22, res-pectively. The tubes may be supported in the screed assembly as .by the brace partially shown at 46 in FIG. 1 extending between wall 22 and flange 24 and suitably apertured to receive ends of the tubes. Opposite ends of the tubes may 'be interconnected as by bar 48, which may 'be anchored in place as by anchor connection S0 fastened both to the ybar and to an inclined strut 52.

Strut 52 joins with flange 24 and slopes upwardly from the flange to a point of joinder with an elevated part of wall 22. In operation of the screed heater, an ignited combustible gas mixture is delivered into the heat-diffusing tubes to be directed by the tubes into the elongated internal corners that flange 24 and wall 22 define with the screed plate along opposite margins of the screed plate. Flow from the tubes is accommodated by |bores or passages 60 extending through the walls of the tubes. These bores, it will be noted, are provided in outer side portions of the tubes only, and their axes extend obliquely relative to the plane of the screed plate 20. The bores or passages therefore direct hot gaseous material emanating therefrom toward the internal corners as shown by the arrow in FIG. 4, and not directly against the screed plate. These corners, therefore, are the portions of the screed assembly that receive the most direct heating, which is desirable, as a greater mass of metal is present at the corners than along an intermediate portion of the screed plate. Hot gases, after flowing into such corners, then flow within chamber 20 over center portions of the screed plate.

Supplying the hot gases to the heat-diffusing tubes is a `burner indicated generally at 70, having a bottom end connected to and communicating with the interior of a transfer duct 74. The burner is remote from the heatdiffusing tubes, more specifically, mounted above them, and gases emanating from the burner are transferred by duct 74 into the tubes.

Considering burner 70, 80 indicates a sleeve, which has suitably mounted therein (and referring to FIG. a nozzle member 82 containing a jet producing orifice 84. Fuel, such as propane gas, is .supplied from a suitable tank (not shown) and through a flexible hose 86, control valve 88, and pipe 90, to sleeve 80 and the nozzle therein. Fastened to the 'base of the sleeve is a mixer housing 92 apertured as at 94. Gas discharged into the mixer housfin'g is mixed with air passing to the interior of the housing through these apertures to produce a combustible mixture.

The mixer housing is hinged at 96 to a bracket 97 joined to a collecting sleeve 98 forming part of transfer duct 74. Transfer duct 74 further comprises a pair of legs 100, 102 which are hollow and may be of substantially rectangular outline as illustrated, such legs flaring outwardly progressing downwardly from the collecting sleeve. The legs communi-cate at their top ends with the interior of the collecting sleeve, and wall portions 104, 106 of the legs function as a divider whereby material passing down through the collecting sleeve may 'be divided into substantially equal portions flowing downwardly through each leg. The legs at their lower extremities are joined to tubes 40, 42, with their interiors communicating with the interiors of these tubes.

The mixer housing is connected to the collecting sleeve on the side opposite where hinge 96 is located through a pivoted clasp member 110 with a lower end that ts about a lug 112. With the clasp member swung to the left in FIG. 3, one side of the mixer housing is disconnected from the collecting sleeve which enables the burner to be swung bodily as indicated by the dashed outline in FIG. 3. This opens up the base of the collecting sleeve and exposes orifice 84 in the nozzle whereby lighting of the yburner is facilitated.

Covering the heat-diffusing tubes at the base of the heater is a cover plate 114 joined in a suitable manner to flange 24 and extending to adjacent wall 22. The cover contains a cut out 116 through which extends transfer duct 74, At 118 is indicated an expanse in the cover which inclines upwardly progressing from flange 24 to adjacent wall 22, and which extends over the strut and other structure described which hold one set of ends of the heat-diffusing tubes.

The cover plate is not completely tight around all margins with the screed assembly. Gases may escape from under the cover lby passing through space 120 between the legs of a transfer duct. Gases may also escape around margin 122 of the cover, which is spaced somewhat from wall 22, and up through the chimney or chute defined by expanse 118 at the cover at a set of ends of the heat-diffusing tubes.

Screed heater 18 adjacent the other end of the screed assembly in all material respects may `be the same as the screed heater just described. Cover 114 extends over the heat-diffusing tubes of this other screed heater in the same way as that described in connection with heater 16. The cover thus forms a substantially closed chamber of chamber 29 housing the various heat-diffusing tubes, which serves to retain hot gases over the top of the screed plate. Cover 114 promotes the circulation of hot gases from the internal corners adjacent margins of the screed plate to central portions of the screed plate.

Along the rear of the screed plate, and mounted in a suitable manner adjacent the ends of the screed assembly, as by hinges 124, is a catwalk 126. This includes a grate 128 over the top thereof, provided to support an operator of the paver. The grate provides ventilation, and thus the heat of the screed heaters is not `transmitted to the catwalk.

The heating means described produces fast even heating of the screed plate, with substantially no buckling or bending therein. With margins of the screed plate subjected to the most direct heating, any expansion that may result from the heating tends to tension portions of the screed plate between the margins. The heat-diffusing tubes in a heater collect hot gases flowing from the burner, and direct streams of these gases laterally outwardly thus to avoid localized heating of the top of the screed plate.

The screed heaters are readily ignited through the expedient of opening the valve described, swinging the burner on its hinge mechanism, and placing a flame adjacent the jet orifice in the nozzle. With the fuel lighted, the burner may be swung down and clamped into place, with hot gases then traveling through the collecting sleeve and legs to the heat-diffusing tubes.

While an embodiment of the invention has been dcscribed, it is not intended to be limited strictly thereto, as various changes and variations are possi-ble without departing from the invention. It is desired to cover all such modifications of the invention as would be apparent to one skilled in the art, and that come within the scope of the appended claims.

It is claimed and desired to secure `by Letters Patent:

1. In a paving machine including an elongated screed plate for leveling and smoothing paving material,

upstanding walls extending longitudinally along opposite sides of the screed plate, joined thereto, and forming opposed internal corners with the top and longitudinal side margins of the screed plate,

an elongated heat-diffusing conduit for each of said corners, mounted on the top of and extending along the length of the screed plate adjacent the corner, passages in the wall of each of said heat-diffusing conduits, in side portions of the conduit, extending obliquely relative to the plane of the top of the screed plate, and accommodating the ow of hot gases out of the conduit, with such gases directed toward a corner,

burner means remote from said heat-diffusing conduits including a mixer housing for producing a mixture of combustible gases, and

a transfer duct connecting said burner means and heatdiffusing conduits.

2. In a paving machine including an elongated screed plate for leveling and smoothing paving material,

an upstanding wall extending longitudinally along a side of the screed plate, joined thereto :and forming an internal corner with the top and longitudinal margin of the screed plate,

an elongated heat-diffusing conduit for said corner, mounted on the top of and extending along the length of the screed plate adjacent the corner,

passage means in the wall of said conduit extending towards said corner enabling hot gases to escape the conduit and operable to direct such gases into the internal corner which is adjacent the conduit,

a burner mounted above said conduit including an orifice for the admission of fuel as a jet to theburner, and an apertured mixer housing receiving such fuel and operable to mix air with the fuel to produce a mixture of combustible gases, and

a transfer duct connecting the mixer housing and said heat-diffusing conduit.

3. In a paving machine including an elongated screed plate for leveling and smoothing paving material,

an elongated heat-diffusing conduit mounted on the top of the screed plate, having an outer end adjacent one end of the screed plate and extending in a longitudinal direction from adjacent said one end of the plate to a point intermediate the ends of the plate,

a second elongated heat-diffusing conduit mounted on the top of the screed plate, extending in a longitudinal direction from the other end of the plate to a point intermediate the ends of the plate,

passages in the walls of such conduits, in side portions thereof, extending obliquely relative to the plane of the top of the screed plate, accommodating the flow of hot gases out of the conduits,

a burner for each heat-diffusing conduit, remote from the conduit, and including an orifice for the admission of f-uel as a jet to the burner, and an apertured mixer housing receiving such fuel and mixing air therewith to form a mixture of combustible gases, and

a transfer conduit for each heat-diffusing conduit connecting the conduits burner to the conduit at a location adjacent its outer end.

4. In a paving machine including an elongated screed plate for leveling and smoothing paving material,

upstanding walls extending longitudinally along opposite sides of the screed plate, joined thereto, and forming opposed internal corners at the top and longitudinal margins of the screed plate, and a screed heater over said screed plate between said walls, said screed heater comprising an elongated heat-diffusing conduit for each of said corners mounted on the top of and extending along the length of the screed plate adjacent the corner,

passage means in the wall of each conduit enabling hot gases to escape the conduit and operable to direct such gases into the internal corner which is adjacent the conduit,

a transfer duct connected to the lheat-diffusing conduits comprising a pair of legs, one connected to each conduit, projecting upwardly from the conduit, and a collecting sleeve above and communicating with said legs, and

a -burner mounted on the top of said sleeve including an orifice for the admission of fuel as a jet to the burner and an apertured mixer housing receiving fluel from said jet operable to mix air with the fuel and produce a mixture of combustible gases, said burner having its mixer housing communicating at the base thereof with said collecting sleeve.

5. The paving machine of claim 4, wherein said burner is supported over said sleeve by means of a hinge, and said hinge accommodates pivoting of the burner to one side whereby the base of the mixer housing is opened up and the jet orifice in the burner exposed.

6. The paving machine of claim 5, wherein a pair of such screed heaters are provided, one adjacent each end of the screed plate, and wherein a cover extends over the tops of the heat-diffusing conduits in the screed heaters forming a common heat-retention chamber bounded by said walls, cover, and the screed plate.

7. In a paving machine including an elongated screed plate for leveling and smoothing paving material, at least one upstanding wall extending longitudinally along a side of the screed plate and joined thereto, said wall forming an internal corner with the top and longitudinal side margin of the screed plate,

an elongated heat-diffusing cond-uit mounted on the top of the screed plate and extending along the length thereof adjacent said corner,

passages in the wall of said heat-diffusing conduit, in side portions thereof, extending toward said corner and obliquely relative to the plane at the top of the screed plate, said passages accommodating the ow of hot gases out of the conduit with such being directed toward said corner,

burner means where ignition of fuel takes place including a mixer housing for producing a mixture of combustible gases, and

a transfer duct connecting said burner means and said heat-diffusing conduit.

References Cited by the Examiner UNITED STATES PATENTS 502,370 8/1893 Lied 126-360 1,049,461 1/ 1913 Diskin l26-360 2,303,812 12/1942 Barber 9'4-45 2,947,230 8/ 1960 Heer 94-46 2,951,426 9/1960 Pollitz 94-46 JACOB L. NACKENOFF, Primary Examiner.

Dedication 3,286,606.-Jae/: I). La7/tow, Salom, 0mg. HEATEI) SCREED ASSEMBLY.

Patent dated Nov. 2i 1966. Dedication filed Feb. 2, 1972, by the assignee, Lag/on lllmzufeetwvng U0.

Hereby dedicntes to the Public the entire remaining term of said patent.

[Oyez'al Gazette December 26', 1.972.] 

1. IN A PAVING MACHINE INCLUDING AN ELONGATED SCREED PLATE FOR LEVELING AND SMOOTHING PAVING MATERIAL, UPSTANDING WALLS EXTENDING LOGITUDINALLY ALONG OPPOSITE SIDES OF THE SCREED PLATE, JOINED THERETO, AND FORMING OPPOSED INTERNAL CORNERS WITH THE TOP AND LONGITUDINAL SIDE MARGINS OF THE SCREED PLATE, AN ELONGATED HEAT-DIFFUSING CONDUIT FOR EACH OF SAID CORNERS, MOUNTED ON THE TOP OF AND EXTENDING ALONG THE LENGTH OF THE SCREED PLATE ADJACENT THE CORNER, PASSAGES IN THE WALL OF EACH SAID HEAT-DIFFUSING CONDUITS, IN SIDE PORTIONS OF THE CIUDUIT, EXTENDING OBLIQUELY RELATIVE TO THE PLANE OF THE TOP OF THE SCREED PLATE, AND ACCOMMODATING THE FLOW OF HOT GASES OUT OF THE CONDUIT, WITH SUCH GASES DIRECTED TOWARD A CORNER, BURNER MEANS REMOTE FROM SAID HEAT-DIFFUSING CONDUITS INCLUDING A MIXER HOUSING FOR PRODUCING MIXTURE OF COMBUSTIBLE GASES, AND A TRANSFER DUCT CONNECTING SAID BURNER MEANS AND HEATDIFFUSING CONDUITS. 